Eelektross

Eelektross looks pretty cool and is an interesting addition to Pokemon Go, but at the time of its release multiple superior Electric-types have already been introduced to the game. While Eelektross is not a bad Pokemon, the fact that there's better existing options makes Eelektross unfortunately not much more valuable than a dex entry. 

Best PvE Offensive Moveset

• Spark benefits from STAB and helps to fulfill an Electric-type role. Volt Switch* falls behind a bit, and is also terrible for dodging.
• Acid doesn't have much use.
• Thunderbolt is the best (and only) recommended charge move for this electric eel on offense.
• Dragon Claw can be used frequently as a 3-bar move to deal consistent damage, but lacks STAB and synergy. 
• Crunch and Liquidation fall behind in performance and don't have any real use on offense.
• Acid Spray is for PvP. 

Best PvE Defensive Moveset

• Volt Switch* has amazing defensive presence, and is the top pick.
• Spark and Acid both perform similarly on defense, as Ground-type attackers shrug off either with their resistances. 
• Liquidation comes out frequently, hits hard, and has coverage against Elektross' only weakness. It's the charged move of choice.
• Crunch is largely unresisted and can be spammed frequently as a 3-bar move, but lacks STAB. 
• Dragon Claw deals slightly less damage but is slightly harder to dodge. 
• Thunderbolt would be doubly resisted by Ground-type attackers and is toothless in that scenario.
• Acid Spray is meant for PvP. 

Eelektross's Community Day move, Volt Switch, boasts superior damage and energy compared to Spark. Acid is not worth mentioning.

Dragon Claw serves as Eelektross's cheapest Charged Attack option and provides general coverage, especially against opposing Dragon-type Pokemon. Liquidation can pressure Ground-type Pokemon, though Eelektross likely won't win against them head-on. Crunch provides a different coverage and can debuff its opponents. Thunderbolt is Eelektross's strongest option and helps make its Electric-type damage more reliable, but sacrifices coverage in the process. Acid Spray is an interesting debuffing option, but due to its low damage output, it is often best left to Pokemon who deal heavy Fast Attack damage.